The major goal of this proposal is to standardize the technique such that oxygen can be accurately quantified throughout the eye. This involves each of the main compartments within the eye, namely, the aqueous, lens and vitreous. In the process of these studies we will determine the viscosity of the lens, which is essential to determining the diffusion of oxygen and nutrients in that tissue. Oxygen levels are not only crucial to the health of different ocular tissues, but also changes in the concentration of oxygen are involved in the etiology of diseases such as cataract or AMD. It is, therefore, important to study oxygen levels in various positions and structures within the eye under normal and disease conditions. To date, the primary method of measuring oxygen is the utilization of physical probes such as oxygen electrodes or optodes. These have the disadvantage of damaging the eye itself or of the probes becoming damaged while being inserted into the eye. In conjunction with Bruce Ishimoto of Ocumetrics, we have modified a Fluorotron Ocular Fluorometer such that it can now detect phosphorescence from an oxygen sensitive palladium porphyrin (eg. PdUp palladium uroporphyrin). This instrument is capable of scanning through the entire eye and detecting oxygen throughout that tissue in a continuous manner. Using this instrument, we propose the following specific aims: I) To evaluate, characterize and quantify phosphorescence from various ocular structures using the Fluorotron. In conjunction with these studies, we will determine the viscosity of the lens, which is important in the diffusion of nutrients and oxygen within the lens. II) To apply this to a rabbit model. Again the values will be compared to those obtained using an optode, which is a method that we have successfully used before (see appendix 2). III) After a vitrectomy the vitreous is replaced by various solutions that are at atmospheric oxygen. In the course of these studies we will investigate the putative chemical processes involved in the reduction of oxygen tension in the vitreous and the levels of those anti-oxidants in human vitreal samples. The development of this technique will greatly expand our knowledge of the diffusion of oxygen throughout the eye and its possible role in the etiology of disease. PUBLIC HEALTH RELEVANCE: Oxygen levels are not only crucial to the health of different ocular tissues, but changes in the concentration of oxygen are also involved in the etiology of diseases such as cataract or AMD. It is, therefore, important to study oxygen levels in various positions and structures within the eye under normal and disease conditions. To date, this has been done primarily by means of physical probes that can either damage the eye itself or that can undergo damage themselves while being inserted into the eye. We propose to develop a noninvasive technique that will allow accurate quantification of oxygen throughout the eye. The development of this technique will greatly expand our knowledge of the diffusion of oxygen throughout the eye and its possible role in the etiology of disease, which has considerable implications for public health. These studies will eventually lead to the development of methods to control oxygen levels within the eye.